Microscopic mechanism of XCQ16 and 20Mn2 axle steel fatigue failure
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摘要: 利用掃描電鏡(SEM)對XCQ16和20Mn2兩種車軸用鋼疲勞斷口和裂紋擴展斷口進行分析,研究疲勞失效過程中的裂紋萌生及擴展機理.結果表明:裂紋均是從試樣表面萌生,非金屬夾雜和位錯是主要的萌生機制;XCQ16鋼在疲勞斷口中部區的裂紋閉合效應大于20Mn2鋼,裂紋擴展較慢;兩者在裂紋擴展區的擴展機理不同,XCQ16鋼屬于塑性斷裂,20Mn2鋼屬于解理斷裂;在非金屬夾雜上,XCQ16鋼多含氧化物和硫化物的混合夾雜,20Mn2鋼主要是氧化物夾雜,混合夾雜對材料的疲勞性能影響較小.Abstract: The fatigue fracture and crack propagation of XCQ16 and 20Mn2 axle steel were observed by SEM. Based on the observed results, the mechanisms of fatigue crack initiation and propagation were studied. It is shown that cracks initiate from the sample surfaces. The main mechanism of crack initiation is non-metallic inclusions and dislocations. The crack closure effect of XCQ16 steel is stronger than 20Mn2 steel in crack propagation areas, leading to a lower crack growth rate. The fracture mechanisms of the two steels are different:plastic fracture for XCQ16 and cleavage fracture for 20Mn2. Non-metallic inclusions in XCQ16 are composed of oxide inclusions and sulfide inclusions, but mainly oxide inclusions in 20Mn2 steel. The mixed inclusions in XCQ16 steel have less effect on its fatigue property.
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